The work processing such as ion plating and plasma etching is carried out in a clean environment and in a high vacuum for a fabrication of a semiconductor such as a silicon wafer, a thin film, and liquid crystal.
As a valve structure for opening and closing an open part that requires an high air-tightness and that a processed substance such as a silicon wafer can be easily transferred into and from, a bonded-type gate valve for vacuum is publicly known.
For instance, the bonded-type gate valve for vacuum has advantages that a sealing performance is higher and a repeated opening and closing operation property is excellent as compared with a conventional seal apparatus in which a seal member is simply mounted in a dovetail groove formed in a plate body.
The plate body is made of a metal such as aluminum, and a seal member made of fluoro-rubber or the like is bonded to the plate body.
FIG. 6 shows a conventional gate valve for vacuum disclosed in Patent document 1. The gate valve for vacuum is disposed for instance on a gate opening section 16 for wafer transfer between a process chamber 2 and a transfer chamber 4.
A gate valve 6 for vacuum is composed of a plate body 8 made of a metal formed in a generally rectangular shape and a seal member 10 made of an elastic material bonded to the peripheral section of the plate body 8. The plate body 8 is fixed to a base 12 having a cross section in a generally L shape. A vertically movable axis or the like 14 is fixed through the center of the base 12 in the longitudinal direction.
In the case in which the gate valve 6 for vacuum has a configuration for opening and closing the gate opening section 16 by only a vertical movement of the axis 14, a sliding causes the plate body 8 to be easily scratched and metal particles to be produced. Consequently, the plate body 8 is pulled to the left in the drawing and is then moved vertically. More specifically, to close the gate opening section 16 in an open state with the plate body 8 being disposed at a lower position, the axis 14 disposed at a lower position is moved to a direction of an arrow X and the plate body 8 is then moved to a direction of an arrow Y. As a result, the seal member 10 is pressed to a valve seat surface 18 formed on the peripheral section of the gate opening section 16 to seal the process chamber 2 closely.
As shown in FIG. 7, for the gate valve 6 for vacuum, a cross-sectional shape of the seal member 10 mounted to the plate body 8 is a generally chevron shape, and a cross-sectional shape of a seal member mounting groove 23 formed on the plate body 8 is an L shape in which an end of the outer side is opened.
The most protruding apex T of the seal member 10 is positioned on the outer side from the center position C of S/2 (right side in FIG. 7), where the width of the bottom surface of the seal member mounting groove 23 is S. That is, A is larger than B.
For the seal member 10 of the gate valve 6 for vacuum, an outer sloped surface 26 is formed on the outer side from the apex T, and an inner sloped surface 28 is formed on the inner side from the apex T. A curve 30 in an arc shape is formed between the outer sloped surface 26 and the inner sloped surface 28.
An inclination θ2 of the inner sloped surface 28 against to the bottom surface of the seal member mounting groove 23 is larger than an inclination θ1 of the outer sloped surface 26. That is, θ2 is larger θ1.
As described above, the seal member 10 in which the apex T and the inclinations θ1 and θ2 are set is bonded to the seal member mounting groove 23 of the plate body 8 with an adhesive agent. The plate body 8 provided with the seal member 10 is disposed between the process chamber 2 and the transfer chamber 4 shown in FIG. 6. The seal member 10 in the plate body 8 is abutted to a wall 21 configuring the gate opening section 16 and compressed in the Y direction by degrees. As shown by an arrow Z in FIG. 8, the seal member 10 is then deformed in such a manner that the seal member 10 is swelled outside from the seal member mounting groove 23. As shown in FIG. 8, an end 10a of the seal member 10 is deformed in such a manner that a part of the seal member 10 hangs out of the seal member mounting groove 23. In the case in which the deforming movement is carried out repeatedly in the state that a part of the seal member 10 hangs out of the seal member mounting groove 23, the adhesive agent is separated. In the case in which the seal member 10 is repeatedly compressed and deformed after the adhesive agent is separated, a stress concentration is applied to the section abutted to the corner of the plate body 8, thereby easily generating a crack 24 in the section. In the case in which a compressive load is applied to the seal member 10 repeatedly after the crack 24 is generated, the crack 24 is grown by degrees. As a result, the seal member 10 is damaged disadvantageously. Even if the seal member 10 is not damaged, particles are produced unfortunately.
Moreover, the rub of the apex T of the seal member 10 with the opponent surface during deformation causes particles to be produced disadvantageously.
Patent document 1: Japanese Patent Application Laid-Open Publication No. 2005-252184